1. Field of the Invention
The invention relates to gas turbine shaft bearing system service method and a gas turbine shaft bearing system service tool that facilitates axial sliding movement of the bearing system bearing and seal assemblies on the shaft during removal and installation service. The tool causes the bearing system bearing and seal assemblies to slide relative to the shaft by application of axial biasing force between the axially fixed position shaft and the bearing or seal of the bearing assembly within the bearing housing envelope. The tool is preferably operable without the need for external fixtures for application of the bearing or seal sliding biasing force, so that it can be man portable and operable within confined field installation spaces.
2. Description of the Prior Art
Industrial gas turbine rotor shafts are supported on bearing systems, including for example an exhaust bearing system within a bearing housing of a single piece exhaust (“SPEX”). A bearing system comprises a seal inboard within the bearing housing and a bearing outboard within the housing that have axially tandem positions circumscribing the rotor shaft. During scheduled turbine shut downs bearing assemblies are removed and replaced in the field installation. It is desirable to return a gas turbine to service as soon as reasonably possible so that it can generate power for the electric grid.
The schematic drawing FIGS. 1-3 show a known gas turbine single piece exhaust (SPEX) 30 tunnel having an external mounting flange 31. Bearing housing 32 is oriented within the tunnel and has a bearing housing end surface 34 and bearing recess 36 in which is retained the slidably moveable bearing system assembly 38A that includes the inboard mounted seal 38B and bearing 38. The bearing assembly 38A separate bearing 38 and the seal 38B are removed and installed serially in the same way by the tool and method embodiments of the present invention. For conciseness of this description, future reference to the bearing system 38A will be focused on the bearing assembly 38, but it should be understood that the same tools and methods are applicable to installation and removal of the seal 38B of the same bearing system 38A. Turbine rotor shaft 40 is supported in the bearing assembly 38 of the bearing system 38A, and has an end face 42 that often includes threaded apertures 44. The bearing 38 is removed and installed with an external bearing replacement fixture 50, which includes a massive sled 52 that rests on the gas turbine pad support structure. The sled 50 supports a hydraulic unit 54 that with hydraulic pump 55 generates the axial biasing force needed to remove and install the bearing assembly 38. A bearing skid 56 may be utilized to bridge the gap between the bearing housing 32 and the sled 52, to provide a convenient resting surface for the bearing assembly 38 prior to it insertion on or removal from the shaft 40. A bearing puller ring 57 is affixed to the external axial face of the bearing assembly 38. The bearing puller ring 57 is coupled to bearing puller rods 58, which are in turn coupled to the hydraulic unit 54 for exerting a pulling or tensile biasing force that extracts the bearing assembly 38 from the bearing recess 36 and the shaft 40. When the bearing assembly 38 is separated from the shaft 40 it may be placed on the bearing skid 56. For bearing reinstallation, the bearing assembly 38 is inserted over the shaft 40, if desired with the assistance of the bearing skid 56, and compressively biased into the bearing recess 36 by interposing stiff slender members between the bearing assembly and the hydraulic unit.
An alternative embodiment of a known self-supporting bearing skid 60 is shown in FIG. 2, which comprises a pair of bearing support tubes 62 flanking left and right sides of the bearing assembly 38 to provide resting surfaces. Each bearing support tube 62 is coupled to the bearing housing end surface 34 by long screws 64 or threaded rods with mating nuts (not shown). Bearing support tube truss 66 is coupled to the turbine exhaust flange 31. The bearing skid 60 is attached directly to the turbine exhaust housing 30 as a free standing unit without the need to support an end on the turbine sled 52. In this way the turbine sled 52 may be maneuvered independent from the bearing skid 60, allowing more positioning flexibility in the field.
In a manufacturing or remote service facility the replacement fixture 50 and sled 52 may be permanently mounted on the factory floor, with the gas turbine moved to different locations within the factory for different fabrication or service operations. In an operational power generating plant field environment the bear replacement fixture 50 including the massive sled 52 are brought to the site and placed on the turbine pad support structure with cranes or hoists within a relatively confined service space that is populated by piping, cables and other power generation equipment. The sled 52 is too large and bulky for man-carrying portability, as it must have sufficient mass to avoid inadvertent movement as the hydraulic unit exerts axial biasing force to insert or remove a bearing assembly 38.
Thus, a need exists in the art for a man-portable gas turbine bearing service method and service tool that can be carried to a field site and installed directly in the bearing housing without the need for cranes or hoists. Advantageously the man-portable gas turbine bearing service tool components are sufficiently small so that they can be readily maneuvered within relatively tight confines of a gas turbine support pad service space.